In the above-identified U.S. patent, there is shown and described a thick sleeve-like seal member through which a valve control stem extends, the seal member having a transverse flow passage having an enlargement or atrium to form inner and outer lips flexed under the influence of line pressure to assist in providing a seal. The inner lip engages the peripheral surface of the control stem in the OFF position and the outer lip engages about the supply port. Flow is controlled by moving the stem axially until a relieved portion is opposed to the seal member passage. A cage supports the seal member to restrain the inside lip against excessive inward movement. The lip has a bead at its edge that projects through a corresponding cage aperture in order to achieve the required engagement with the control stem at the OFF position.
In the manufacture of such resilient seal members, a certain small percentage tend to deflect very slightly at the region of the inner lip so that, upon application of line pressure, an imperfect static seal exists as water enters behind the bead. A net hydraulic pressure never builds sufficiently up in the atrium. The result is a defective valve. Of course the valves are factory tested. But a reject rate of even one per hundred is costly. There is no known fast, simple method of advance testing the seal members themselves.
The primary object of this invention is to provide a simple structural arrangement that obviates individual testing of the seal members and that results in a reliable valve that performs satisfactorily notwithstanding slight dimensional variations in the seal member.